In orthopedic surgery, intraoperative fluoroscopic images are extensively used in order to ascertain the alignment of orthopedic implants, such that they are inserted into their predetermined positions, as selected by the surgeon generally using preoperative three-dimensional images, such as CT images. Such intra-operative fluoroscopic images are also used in order to ascertain that the orthopedic implants have been inserted into their correct position at the conclusion of the operation. However, such verification may be difficult to perform since although the implants, generally being metallic, show up with high contrast in the intra-operative x-ray images, the anatomical features around them may have much weaker contrast, and, because of the depth of soft tissue and bone through which the x-ray image is being taken, various image artifacts may make the X ray image difficult to interpret. Consequently, in the typically blurred fluoroscope image, it may be difficult to associate the position of the implant with the unclearly defined surrounding bone structure into which the insert has been placed. Currently this is a problematic situation, since the verification of an implant location can only be performed after closing the operating site, and sending the patient for a high definition 3-D imaging procedure, such as a CT or an MRI procedure, in which the soft tissues and bone are also clearly defined. If this procedure shows that the implant is not in the correct position, then the patient must undergo a correction operation, with its associated discomfort and costs.
This problem is particularly acute in spinal operations, such as those which use pedicle screws for spinal fusion for instance, the accuracy of the placement of the screws being highly critical because of the proximity of sensitive neurological features. Because of the complex orthopedic structural nature of the vertebrae themselves and of their associated muscles and ligaments, determination of the spatial position and angle of a pedicle screw is difficult to define in a two-dimensional x-ray image.
There therefore exists a need for an imaging technique which enables the verification of the accurate 3D positioning of an insert during the operation itself, such that it overcomes at least some of the disadvantages of prior art methods.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.